Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$148.31	13.709%	$168.6418	$168.64	$168.65	$168.60
Purchase #2	$239.45	6.839%	$255.826	$255.83	$255.85	$255.80
Purchase #3	$43.55	7.402%	$46.7736	$46.77	$46.75	$46.80
Purchase #4	$42.29	3.194%	$43.6407	$43.64	$43.65	$43.60
Purchase #5	$22.52	10.268%	$24.8324	$24.83	$24.85	$24.80
Purchase #6	$210.90	13.209%	$238.7578	$238.76	$238.75	$238.80
Purchase #7	$232.70	13.869%	$264.9732	$264.97	$264.95	$265.00
7 purchase totals =	$939.72		$1,043.4455	$1,043.44	$1,043.45	$1,043.40